The influence of carbon based coatings and surface finish on the tribological performance in high-load contacts

The effect of surface finish with two types of carbon based coatings was evaluated in rolling contact twin disc tests. The surface finish grades represented the ground surface, and two polished surfaces providing average surface roughness values of Ra 0.128 μm and 0.030 μm. The twin disc test parameters were selected to represent the contact parameters of practical gear contacts with the maximum contact pressure of 1.7 GPa. The micropitting could be prohibited by polishing the surfaces or by using surface coatings. With the optimised combination of surface roughness and carbon coating the reduction of 27% in friction coefficient could be achieved with improved wear performance in twin disc tests.